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Issue 13:     23 March 2006
Latest News

Welcome to the CDS Newsletter. The goal of this Newsletter is to inform the CDS user community of
  • current CDS science topics
  • developments in CDS data analysis
  • instrumental matters
  • operational issues
We invite your contributions on CDS-related matters: data analysis, science results, instrument calibration, software and questions on these topics. Your responses will influence the content of future issues. Please send newsletter inputs and correspondence to the editor, A.Fludra(at)

Happy 10th Anniversary, CDS!


Retirements & Staff Changes

We are sad to announce that three members of the CDS team at RAL, Jeff Payne, Jim Lang and Barry Kent are retiring at the end of March.

Jeff Payne joined the CDS team some years before launch and has served as the CDS Instrument Manager and Ground Systems Manager throughout the mission. He has been our top instrument expert, ensuring smooth running of CDS through continuous monitoring of instrument health and operations, interfacing to the Goddard operations personnel, and interacting with the user community.

Jim Lang was involved in the pre-launch calibration of the CDS, played a leading role in writing up the results and subsequently has refined the calibration throughout the mission as one of the key players in the cross-calibration rocket flights and in synoptic data analysis. He has been very much the CDS team expert in atomic physics and spectroscopic matters, frequently interacting with the user community. He is also well known for his own research interests in solar atomic physics.

Barry Kent also played a major role in the CDS calibration - he has been the hands-on experimentalist in charge of the Blue Tank calibration facility at RAL, which has become well known for the calibration of not only CDS, but the EIS/Solar-B instrument, MOSES, SERTS and EUNIS. He has in effect constructed and run a facility from which the solar community has greatly benefited.

We will miss all three of them and wish them best of luck in their retirement. The role of the CDS Instrument Manager at RAL will be taken over by Andy Matheson, and we welcome him to the team. The Blue Tank facility will continue to be run at RAL.

       Andrzej Fludra and Richard Harrison

10 Years of SOHO Celebration
Andrzej Fludra

SOHO 10th Anniversary Celebration was held at RAL on 2nd December 2005. The celebration consisted of a set of short talks describing the history and results from SOHO. The audience included the press, those involved in building hardware for SOHO in the UK, representatives from the UK funding agencies, and representatives from the wider solar physics community.
Alan Gabriel - 'The birth of SOHO – the World’s Flagship Solar Observatory’
Richard Harrison - 'Revolutionising Our View of the Sun – Summary of Results from SOHO’
Andrzej Fludra – 'CDS – The UK’s Solar Toolbox’
Len Culhane – ‘Exploring the Sun - The UK’s Heritage’

'Highlights from CDS' session at the UK Solar Physics meeting
Andrzej Fludra

A special session to mark the 10th anniversary of the Coronal Diagnostic Spectrometer will be held during the UK Solar Physics meeting in Aberystwyth, 10-13 April 2006. The session will consist of contributions from CDS users, presenting their favourite results obtained from the CDS data over the entire SOHO mission.

NASA extends SOHO funding
Andrzej Fludra

The NASA Senior Review panel has approved the extension of the SOHO funding until the end of 2009. The panel has also endorsed the plan of a further extension for 2010 – 2014 in a scaled-down configuration (LASCO coronagraph + European instruments). Application to ESA for SOHO extension will be made in March and our application to PPARC for the extension of the CDS funding is due by mid-September.

Report on the CDS Users Meeting, 21-22 September 2005
Andrzej Fludra

A CDS Users meeting took place in Abingdon, UK on 21 and 22 September 2005. The meeting included discussions of the recent science results and highlights from CDS, exploration of the 9-year SOHO/CDS data archive, updates on practical issues relevant to the CDS data analysis.
Power Point presentations can be downloaded through the highlighted links:

Looking for the CME onset: A ten year CDS campaign - Richard Harrison

Sunspot studies in Oslo with CDS, SUMER, MDI and TRACE - Olav Kjeldseth-Moe

Active regions - Helen Mason

Active region heating. Coronal waves - Sarah Matthews (1)

Flows in flares - Sarah Matthews (2)

Imaging active region transition region with the CDS wide slit - Mike Marsh

Active region loop studies in Oslo - Terje Fredvik

Chromospheric evaporation in solar flares - Peter Gallagher

CDS observations of flares - Giulio Del Zanna (1)

Coronal heating in active regions - Andrzej Fludra

The solar uv lines of He I and He II: effects of photon scattering - Carole Jordan

Coronal hole studies at UCLAN - Barbara Bromage

Dynamics of the polar off-limb regions - Dipankar Banerjee

Quiet sun intensity distributions - Jack Ireland

EUV spectral irradiances from 1996 to 2003 - Giulio DelZanna (2)

CDS calibration summary - Jim Lang

Element Abundance Results from CDS - Peter Young

Using GIS - Lucie Green

Solar-B/EIS - Sarah Matthews

Joint EIS/CDS science – discussion - Helen Mason

Tips and tricks for analysing CDS data - Peter Young

CDS calibration update
Giulio Del Zanna

As already reported at the 2005 CDS user meeting, during the last year I have been carrying on a comprehensive analysis of CDS data during the last 10 years, to extend the early in-flight calibration of all 9 CDS channels (Del Zanna et al. 2001, A&A, 379, 708-734). The main CDS datasets considered are: NIS synoptic and full-Sun data, GIS spectral atlases, complemented with data from other instruments. The preliminary results are very encouraging, showing that all the CDS channels have been remarkably stable over this long period. Several adjustements are however needed. More information will soon be available. I recommend a limited use of the wide slit in conjunction with the NIS, considering the significant decreases in sensitivity due to its use.

GIS Status Report
Paul Kuin

1. Introduction

The GIS has recently been found to be in need of a tune-up.  In particular, detector 1 has been producing spectra that are not good in several wavelength regions. In reality the GIS had been working so well, that the same parameter settings for the on-board processing have been in use for many years, and the voltages used were not increased, or very little.  Now some changes are required.

The best news is that the detectors are capable of excellent work still. It has been found that in many spectral lines the detector sensitivity did not significantly decrease since the start of the mission, although the spectral resolution has gone down.  We have obtained new raw data for the quiet sun, slit 2, at the current settings in February. These are the first raw data taken since 2003.

The GIS website (located at MSSL) has also been refurbished.  As a result, a new guide to GIS data is now available. Recently, the publications related to GIS were updated, and include now some of the early work on the detectors.

The GIS pointing had been giving problems to some users, so an in-depth study was reported by me early January. The GIS has a systematic offset of 20.2 arcsec to the south (for normal roll angle =0) on top of the random uncertainty in the CDS pointing of 2-4 arcsec that was already known from NIS studies. 

2. Status of the detectors and the implications
For all four detectors raw data were obtained in February with  the currently used quiet sun
gset (66) voltages. Based on those data, the following conclusions can be made:
   detectors 3 and 4:
These are the two longer wavelength regions. To tune the detector, we look for an optimum value for the pulse heigh distribution (PHA) of the whole detector of around 100-110 (out of 255). The current peak in the PHA seen in a recent quiet sun raw data transmission was around 70. That means that the detector does not work at 'top efficiency", but the effects may be too subtle to notice. The data continue to be good.

   detector 2:
Detector 2 has a PHA dominated by the He 304 line and can therefore not be optimized in the same way as the other detectors. The detector continues to perform as before.

   detector 1:
The detector voltage has fallen below the operating range. A new gset is being prepared. The wait is determined by the time to obtain raw data at higher voltage. So far the results show that the detector performs just as well as originally, exept for some strong spectral lines suffering from long term gain depression. In April a new gset (for quiet sun) will be installed. The active region gset update will be done next.  For those interested, the raw data and gset fits can be seen on the GIS website.

The following observations can be made of the new raw data. With the current settings, the spectral lines in part of the spectrum become very washed out and ghost into other spiral arms, making the data not useful. However, there are still some good wavelength ranges. The thinnest part of the spiral arms falls still within the gset encoding. So these spectral ranges are in principle useable throughout the past period. They are, generally speaking, the lines that did not show ghosting in the past.  We still need to determine when the data became bad, but indications are that that occurred at or before mid 2005. More details will be published on our web page.

3. A possible new approach
The GIS has different gsets for different levels of activity, because the intensity incident on the detector has an effect on the pulse height distribution. In the data plane the radial positions of the spirals (and the intense lines) shift radially a little bit for high PHA.  That is the reason that a different gset is needed for different activity levels.  We are considering an approach to circumvent that problem, and details will be published on our website.

4. Long-term gain depression 
In 2003 a new study of long term gain depression was completed and the results of that study implemented in the GIS processing. The study was based on observed gain changes when varying detector voltages.  Some questions remained, especially for quiet sun spectra.     We find things that are generally known amongst GIS users, like the line width increase over time, but also that many lines show just small intensity changes.  Only a few stronger lines have a larger loss in intensity.  A report of our findings will be published soon, andmade available on the GIS main website.

5. GIS Support
If you need GIS support, contact the GIS instrument scientist, Paul Kuin, at MSSL. His email is or his solarmail ID is npkuin. His phone number is +44 (0) 1483-204295.

6. Links
  • GIS Website:
  • GIS Publications:
  • GIS Pointing (CDS Software Note #57: ../software/notes.shtml
  • GIS calibration images:
  • GIS status:

User-contributed software
Peter Young and John Rainnie

Do you have your own CDS analysis software that you'd like to share with others? Please send the routines to John Rainnie ( and they will be made available on a special section of the CDS webpage. Following testing they will also be made available through the CDS tree in Solarsoft.

Before submitting, please make sure that the routines are documented. At the least, each routine should have a header giving the name, explanation, inputs/outputs and history. An example can be seen by doing:
IDL> xdoc,'cds_gauss'
An additional file (text/latex/pdf) giving instructions on how to use the routine would also be valuable.

On deriving plasma velocity information from CDS/NIS observations: application to the dynamics of blinkers.
D. H. Brooks & D. Bewsher (Solar Physics - in press)

Using standard instrument software and two independently developed data reduction and analysis procedures, we re-examine the accuracy of plasma velocity information derived from data obtained by the Solar and Heliospheric Observatory (SOHO) - Coronal Diagnostic Spectrometer (CDS). We discuss only the O V 629 A line data obtained by the Normal Incidence Spectrometer (NIS) and analyse a quiet Sun (QS) and active region (AR) dataset. Using the QS data, we demonstrate that the well-known North-South tilt in wavelength along the NIS slit varies significantly with time, which is not accounted for in the standard CDS correction procedures. In addition, when residual N-S trends exist in the data after processing, they may not be detected, nor removed, using the standard analysis software. This underscores the need for careful analysis of velocity results for individual datasets when using standard correction procedures. Furthermore, even when the results obtained by the two independent methods are well correlated (coefficients greater than 0.9), discrepancies in the values of the derived Doppler velocities can remain 95% within +/-5 km/s. Therefore, we apply the results to examine the velocities obtained for EUV blinkers by previous authors. It is found that a strong correlation exists in the patterns of variation of the blinker velocities >~0.98, even though there may be differences in their magnitudes. That is, in a clear majority of cases, the methods agree that a blinker is red-shifted or blue-shifted, although the uncertainty in the absolute velocity may be large.

Properties of a Sunspot Plume Observed With the CDS
J. W. Brosius and E. Landi, 2005, ApJ, 632, 1196

We used three instruments (CDS, EIT, MDI) aboard the Solar and Heliospheric Observatory spacecraft to observe the large sunspot in NOAA Active Region 8539 on 1999 May 9 and 13. The spot contained a bright plume, most easily seen in EUV emission lines formed at 5.2 < log T < 5.7 (where T is the temperature in K), in its umbra on both dates. The plume's differential emission measure (DEM) exhibited one and only one broad peak centered around log T ~ 5.8 on May 9 and around log T~ 5.6 on May 13, and exceeded the DEM of the quiet sun by more than an order of magnitude at these temperatures. The high temperature portion of the plume's DEM resembled that of nearby quiet sun areas. Intensity ratios of the O IV lines at 625.8 A and 554.5 A yield log n_e (where n_e is the electron density in cm^-3) of 9.6^+0.3_-0.6 in the plume on May 9 and 9.7^+0.2_-0.2 on May 13; values of 9.4^+0.3_-0.9 and 9.4^+0.2_-0.3 were obtained in the quiet sun areas on the same dates. Based upon abundance enhancements derived from transition region emission lines of Ca, an element with low first ionization potential, elemental abundances in the plume appear to be coronal rather than photospheric. The plume plasma reveals a bipolar Doppler velocity flow pattern, in which maximum downflows in excess of 37 km/s are observed in the northeast portion of the plume, and maximum upflows that exceed 52 km/s are observed in the northwest.

Thermal Composition and Doppler Velocities in a Transequatorial Loop at the Solar Limb
J. W, Brosius, 2006, ApJ, 636, L57

We observed a transequatorial loop (TEL) connecting NOAA Active Regions 10652 and 10653 at the west solar limb on 2004 July 29 with the Extreme-Ultraviolet Imaging Telescope (EIT) and the Coronal Diagnostic Spectrometer (CDS) aboard the Solar and Heliospheric Observatory. Only the loop’s northern leg was observed with CDS. The loop appeared bright and cospatial in extreme-ultraviolet emission lines from ions formed over a wide range of temperature (T, in kelvins), including He i (log T=4.0), O iii (log T=4.9), O iv (5.2), O v (5.4), Ne vi (5.6), Ca x (5.9), Mg x (6.1), and Fe xii (log T= 6.1). This indicates that the loop plasma was multithermal and covered roughly 2 orders of magnitude in temperature. Our measurement of He i, O iii, and O iv line emission reveals the coolest plasma ever detected in a TEL. The most likely explanation for the wide range of cospatial temperatures in the TEL is that it consisted of numerous sub-resolution strands, all at different temperatures. Each of the lines that are formed at temperatures less than 10^6 K exhibited relative Doppler blueshifts in the TEL that correspond to velocities toward the observer larger than 30 km/s, where the two strongest cool lines (He i at 584.3 and O v at 629.7 ) yielded maximum values of 37 and 41 km/s, respectively. The presence of cool plasma in the TEL at heights several times those of the cool ions’ scale heights suggests that the loop remained visible at low temperatures by maintaining a steady flow of cool plasma.

Radio Measurements of the Height of Strong Coronal Magnetic Fields Above Sunspots at the Solar Limb
J.W. Brosius and S.M. White, 2006, ApJ Letters, (in press, MS# 20411)

We measure coronal magnetic field strengths of 1750 G at a height of 8000 km above a large sunspot in NOAA Active Region 10652 at the west solar limb on 2004 July 29 using coordinated observations with the Very Large Array, the Transition Region And Coronal Explorer, and three instruments (CDS, EIT, MDI) aboard the Solar and Heliospheric Observatory. This observation is the first time that coronal radio brightness temperatures have been analyzed in a 15 GHz solar radio source projected above the limb. Observations at 8 GHz yield coronal magnetic field strengths of 960 G at a height of 12,000 km. The field strength measurements combine to yield a magnetic scale height L_B = 6900 km. The radio brightness temperature maxima are located away from a sunspot plume that appears bright in EUV line emission formed at temperatures around several 10^5 K. We use the density-sensitive emission line intensity ratio of O IV 625.8/554.5 to derive an electron density n_e (in cm-3) of log n_e = 10.1 +/- 0.2 at the base of the plume.

Multi-wavelength observations of the M1 flare of October 22, 2002
Del Zanna, G., Berlicki,A., Mason, H.E., Schmieder,B., 2006, Sol. Phys., 234, 95 - 113

In this paper we present a further study of the M1 class flare observed on October 22, 2002. We focus on the SOHO Coronal Diagnostic Spectrometer (CDS) spectral observations performed during a multi-wavelength campaign with TRACE and ground-based instruments (VTT, THEMIS). Strong blue-shifts are observed in the CDS coronal lines in flare kernels during the impulsive phase of this flare. From a careful wavelength calibration we deduce upflows of 140 km/s for the Fe~XIX flare emission, with a pattern of progressively smaller flows at lower temperatures. Large line-widths were observed, especially for the Fe~XIX line, which indicate the existence of turbulent velocities. The strong upflows correspond to full shifts of the line profiles. These flows are observed at the initial phase of the flare, and correspond to the 'explosive evaporation'. The regions of the blueshifted kernels, a few arc seconds away from the flare onset location, could be explained by the chain reaction of successive magnetic reconnections of growing emerging field line with higher and higher overlying field. This interpretation is evidenced by the analysis of the magnetic topology of the active region using a linear force-free-field extrapolation of THEMIS magnetograms.

The EUV spectral irradiance from 1996 to 2003 as obtained from SOHO
Del Zanna, G., Andretta, V., Beaussier, A., 2005, Mem. Sait., 76, 953

We present EUV (150-800 A) radiance measurements obtained with the SOHO/Coronal Diagnostic Spectrometer (CDS) during the period from 1996 to 2003. We complement the CDS measurements with simultaneous SOHO/EIT EUV images. We use the EIT center-to-limb variations to obtain an estimate of the EUV spectral irradiance of the 'quiet Sun' during 1996-2003. We discuss the evolution of the characteristics of the solar corona from minimum to maximum, and show how it becomes progressively hotter.

The EUV spectral irradiance of the Sun from minimum to maximum
Del Zanna, G., Andretta, V., 2006, Mem. Sait., in press

The solar extreme-ultraviolet (EUV, 150-800 Angstroms) irradiance is one of the dominant factors in the formation of the ionosphere of the Earth, via photo-ionisation. Yet, before the launch of the SOHO satellite (1995), the only few reliable measurements at these wavelengths were obtained in the 60's and 70's, mostly with rocket flights. SOHO gives us the unprecedented opportunity to study in detail the variations of the EUV spectral irradiance from minimum (1996) to maximum (2001-2002) and beyond. We present here a progress-report on a long-term plan to study the EUV spectral irradiance and its characteristics. We use observations with the Coronal Diagnostic Spectrometer (CDS) and the EUV Imaging Telescope (EIT) to present the EUV irradiance at selected wavelengths and characterise the contributions of the different solar regions along the solar cycle.

Benchmarking atomic data for astrophysics: Fe~XII
Del Zanna, G., Mason, H.E., 2005, A&A, 433, 731

Highlights for CDS users:

Predicted line intensities and density diagnostics for the strong Fe XII lines observed by CDS are now significantly different. The strong 59.26 nm line is now identified as an Fe XII transition, useful for density estimates. Note that this line is located in the red-wing of the Fe XIX 59.22 nm line (Del Zanna et al. 2002, Adv. Space Res., 30, 551).

We use recently calculated electron collisional data by Storey et al. (2005) for Fe XII (n=3 configurations) to build a model ion to compare to spectroscopic observations of the solar corona and laboratory measurements. We review all the line identifications of the brightest lines, by comparing both wavelengths and line intensities. The presence of blends in different plasma conditions is highlighted. A large number of new energy levels and line identifications are proposed. In particular, we identify the electric quadrupole ^4P_{5/2}-- ^4F_{9/2} transition with the bright coronal line observed at 592.6~\AA, previously unidentified. This line, when observed with the 1242.0, 1349.5 UV forbidden lines, is a good density diagnostic over a large range of electron densities. We also indicate the best spectral lines to be used for density diagnostics or instrument calibration. From various combinations of lines we obtain electron densities that are significantly different from those published in the previous literature. Some examples are provided. The agreement between theory and experimental data in terms of wavelengths, line intensities and level lifetimes is excellent.

P-mode Propagation Through the Transition Region into the Solar Corona I. Observations
M.S. Marsh and R.W. Walsh (ApJ, 2006, v643)

Oscillations have long been observed in the sunspot umbral chromosphere and transition region, connected to global p-mode oscillations. These p-modes are thought to undergo mode conversion to slow magneto-acoustic waves in regions of strong magnetic field. More recently, propagating oscillations have also been observed in solar coronal loops. Using new spectroscopic imaging data at transition region temperatures, combined with coronal imaging, we present direct observations of the propagation of these slow magneto-acoustic p-modes through the transition region and into the solar corona, along the magnetic field. The waves are observed as oscillations in the chromosphere/transition region and propagations in the corona due to the emission scale height of the different temperature lines, combined with the magnetic field geometry.

Figure : Composite TRACE 1600 A (Red), CDS O V (Green), and TRACE 171 A (Blue) image of sunspot AR 10570 on 2004 March 12. TRACE 1600 shows the penumbral boundary, O V shows the bright transition region emission of the sunspot plume and TRACE 171 shows the coronal magnetic loops. The spatial coincidence of the umbra, sunspot plume, and emerging coronal loop system is clearly apparent. A plasma flow is also visible, originating from just outside the eastern edge of the field of view.

RHESSI and SOHO/CDS Observations of Explosive Chromospheric Evaporation
R. Milligan et al. 2006, ApJ Let, 638, 117

Simultaneous observations of explosive chromospheric evaporation are presented using data from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Coronal Diagnostic Spectrometer (CDS) onboard SOHO. For the first time, co-spatial imaging and spectroscopy have been used to observe explosive evaporation within a hard X-ray emitting region. RHESSI X-ray images and spectra were used to determine the flux of non-thermal electrons accelerated during the impulsive phase of an M2.2 flare. Assuming a thick-target model, the injected electron spectrum was found to have a spectral index of ~7.3, a low energy cut-off of ~20 keV, and a resulting flux of >=4x10^10 ergs cm^-2 s^-1. The dynamic response of the atmosphere was determined using CDS spectra, finding a mean upflow velocity of 230+/-38 km s^-1 in Fe XIX (592.23A), and associated downflows of 36+/-16 km s^-1 and 43+/-22 km s^-1 at chromospheric and transition region temperatures, respectively, relative to an averaged quiet-Sun spectra. The errors represent a 1 sigma dispersion. The properties of the accelerated electron spectrum and the corresponding evaporative velocities were found to be consistent with the predictions of theory.

Magnetoacoustic wave propagation in off-limb polar regions
E. O'Shea, D. Banerjee & J.G., Doyle, 2006, A&A, accepted

Using temporal series data from the Coronal Diagnostic Spectrometer (CDS) on SOHO, we study oscillations found in radiant flux and velocity measurements from transition region and coronal spectral lines. We use Fourier techniques to measure phase delays between flux (`intensity') oscillations and between velocity oscillations of different transition region-corona and corona-corona line pairs. We also measure the phase delays between flux and velocity oscillations (I-V). The phase delays measured between different line pairs, when plotted over a -180 degree to +180 degree range, line up along diagonal lines corresponding to measurable and fixed time delays. The slopes of these diagonal lines suggest the outward propagation of waves. Using the measured time delays, we estimate propagation speeds for the different line pairs that indicate that the waves producing the observed phase delays are magnetoacoustic waves propagating at speeds close to the sound speed. In addition, we find that the phases occur at fixed integer frequencies of f/4 (90 deg) and 3f/16 (67.5 deg), instead of the expected interval of f (360 deg), indicating that a `Doppler effect' is acting on the waves, perhaps due to some form of resonant cavity at coronal temperatures. From I-V measurements, we find evidence for fast magnetoacoustic waves to be predominantly present at coronal temperatures, while at transition region temperatures slow magnetoacoustic waves are more common.

Release of CHIANTI v.5
E. Landi, G. Del Zanna, P.R. Young, K.P. Dere, H.E. Mason, M. Landini 2006, ApJ SS, 162, 261

Major features include:
- inclusion of ionization and recombination effects in level population calculation
- photoexcitation from any user-provided radiation field
- software to account for non-maxwellian distribution of velocities
- new data for Fe IX, Fe X, Fe XII, Fe XV (EUV ), important for missions such as SOHO/CDS and SOLAR-B/EIS
- new data for Fe XVII to Fe XXIV (X-rays), important for the analysis of Chandra and XMM-Newton data.
- new data for n=3 to n=3 N-like and O-like transitions (UV )
- new ions (P XIV, XV; Cl II, X, XI, XII, XVII; K V, XVII, XIX; Ca VII, VIII; Co XX; Zn XXIII)
- many existing ion data-sets have been updated
- the software has been improved and speeded considerably.

Access to data, software, and documentation can be obtained through:

Note to CDS users:
we have recently found that the collisional excitation rate for the 5-11 transition in O IV was mistakenly left out, affecting the emissivity of this line (62.58 nm), used to obtain electron densities in the transition region. With the inclusion of the missing excitation rate the densities become lower. This and a few other minor problems have been fixed in the most recent CHIANTI version (5.2), released in March 2006.

Ionization state, excited populations and emission of impurities in dynamic finite density plasmas: I. The generalized collisional–radiative model for light elements
H. P. Summers, W. J. Dickson, M. G. O’Mullane, N. R. Badnell, A. D. Whiteford, D. H. Brooks, J. Lang, S. D. Loch and D. C. Griffin

The paper presents an integrated view of the population structure and its role in establishing the ionization state of light elements in dynamic, finite density, laboratory and astrophysical plasmas. There are four main issues, the generalized collisional–radiative picture for metastables in dynamic plasmas with Maxwellian free electrons and its particularizing to light elements, the methods of bundling and projection for manipulating the population equations, the systematic production/use of state selective fundamental collision data in the metastable resolved picture to all levels for collisonal–radiative modeling and the delivery of appropriate derived coefficients for experiment analysis. The ions of carbon, oxygen and neon are used in illustration. The practical implementation of the methods described here is part of the ADAS Project

Observational Evidence for Gentle Chromospheric Evaporation During the Impulsive Phase of a Solar Flare
R. O. Milligan, P. T. Gallagher, M. Mathioudakis, & F. P. Keenan, 2006, ApJL, accepted

Observational evidence for gentle chromospheric evaporation during the impulsive phase of a C9.1 solar flare is presented using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the Coronal Diagnostic Spectrometer on board the Solar and Heliospheric Observatory. Until now, evidence for gentle evaporation has only been reported during the decay phase of a solar flare, where thermal conduction is thought to be the driving mechanism. Here we show that the chromospheric response to a low flux of nonthermal electrons >=5x10^9 ergs cm^-2 s^-1 results in plasma upflows of 13+/-16, 16+/-18, and 110+/-58 km s^-1 in the cool He I and O V emission 13+lines and the 8 MK Fe XIX line. These findings, in conjunction with other recently reported work, now confirm that the dynamic response of the solar atmosphere is sensitively dependent on the flux of incident electrons.

From the CDS Operations Management Team in the Space Science & Technology Department at CCLRC Rutherford Appleton Laboratory
Site maintained by John Rainnie.
Last revised on Tuesday (22/Jan/2019) at 15:07.